ROMFS: disable esc failure detector for fixed-wing simulations

[MAD-CRAZY-MAN]

Problem

When running SITL simulations for fixed-wing models like rc_cessna or advanced_plane, arming the system in manual or position mode results in an ESC Failure, preventing the system from arming.

Solution

This issue can be resolved by disabling the ESC failure detector (FD_ESCS_EN: 0).

The ESC failure detector monitors the esc_armed_flags from the esc_status topic. In real aircraft, motor output drivers like PX4IO or pwm_out check whether the ESC is actually armed.

However, in a simulation environment, the ESC status is inferred from the actuator's velocity using the gz_bridge module (as implemented in GZMixingInterfaceESC.cpp).
For fixed-wing aircraft, the motor does not spin until the throttle is increased, even when the system is armed. Therefore, it is necessary to disable the ESC failure detector for fixed-wing simulations.

[dagar]

Arguably the real problem is the way we're setting ESC armed here?

PX4-Autopilot/src/modules/simulation/gz_bridge/GZMixingInterfaceESC.cpp

Lines 117 to 119 in ca47f6f

	if (actuators.velocity(i) > 0) {
	esc_status.esc_armed_flags |= 1 << i;
	}

Why don't we just change it so that it's respected armed from the mixer module instead?

[MAD-CRAZY-MAN]

Arguably the real problem is the way we're setting ESC armed here?

PX4-Autopilot/src/modules/simulation/gz_bridge/GZMixingInterfaceESC.cpp

Lines 117 to 119 in ca47f6f

	if (actuators.velocity(i) > 0) {
	esc_status.esc_armed_flags |= 1 << i;
	}

Why don't we just change it so that it's respected armed from the mixer module instead?

Yes, the issue is setting the ESC armed flag based on motor velocity. As you suggested, modifying the mixer module is a better approach. thank you.

I’d like to rectify my previous information.
The px4io and pwm_out modules do not receive esc telemetry data, so they do not publish 'esc_status' topic. Instead, modules like 'dshot', 'gz_bridge' and 'simulator_mavlink' do.

Here`s what i found:

1. The simulator_mavlink module(for JMAVSim and gazebo-classic), whitch performs a similar role to gz_bridge, marks all ESCs as online and armed.
   

   PX4-Autopilot/src/modules/simulation/simulator_mavlink/SimulatorMavlink.cpp

   Lines 164 to 165 in f67eb69

   	esc_status.esc_armed_flags = (1u << esc_status.esc_count) - 1;
   	esc_status.esc_online_flags = (1u << esc_status.esc_count) - 1;

2. Even the dshot module marks all ESCs as online and armed due to a single dropcut issue.
   

   PX4-Autopilot/src/drivers/dshot/DShot.cpp

   Lines 273 to 276 in f67eb69

   	// FIXME: mark all UART Telemetry ESC's as online, otherwise commander complains even for a single dropout
   	esc_status.esc_count = _telemetry->handler.numMotors();
   	esc_status.esc_online_flags = (1 << esc_status.esc_count) - 1;
   	esc_status.esc_armed_flags = (1 << esc_status.esc_count) - 1;

Since using motor velocity for the ESC armed flag is inaccurate and unnecessary for simulations, I`ve updated the system to mark all ESCs as armed, regardless of motor velocity.

[MAD-CRAZY-MAN]

any feedback? @dagar